U.S. patent application number 11/593595 was filed with the patent office on 2007-05-17 for driving and control apparatus of piezoelectric ultrasonic motor.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Burhanettin Koc, Jung Ho Ryu.
Application Number | 20070108869 11/593595 |
Document ID | / |
Family ID | 38040047 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070108869 |
Kind Code |
A1 |
Koc; Burhanettin ; et
al. |
May 17, 2007 |
Driving and control apparatus of piezoelectric ultrasonic motor
Abstract
In a driving and control apparatus of a piezoelectric ultrasonic
motor, a controller controls a selection of a first channel or a
second channel of the piezoelectric ultrasonic motor as a driving
channel. A switch part selects one of the first and second channels
as the driving channel and the other as a detection channel, and
supplies the driving voltage to the piezoelectric ultrasonic motor
through the selected driving channel. A phase detector detects a
voltage outputted from the piezoelectric ultrasonic motor through
the detection channel, calculates a phase deviation, and outputs a
phase difference voltage corresponding to the phase deviation. A
voltage controlled oscillator generates the oscillation voltage and
controls a phase of the oscillation voltage according to the phase
difference voltage. A frequency divider divides the oscillation
voltage by two to generate the driving voltage, and supplies the
divided oscillation voltage to the piezoelectric ultrasonic motor
through the driving channel.
Inventors: |
Koc; Burhanettin; (Sungnam,
KR) ; Ryu; Jung Ho; (Suwon, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon
KR
|
Family ID: |
38040047 |
Appl. No.: |
11/593595 |
Filed: |
November 7, 2006 |
Current U.S.
Class: |
310/316.01 |
Current CPC
Class: |
H02N 2/008 20130101 |
Class at
Publication: |
310/316.01 |
International
Class: |
H01L 41/107 20060101
H01L041/107 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2005 |
KR |
10-2005-0106147 |
Claims
1. A driving and control apparatus of a piezoelectric ultrasonic
motor, the piezoelectric ultrasonic motor having a first electrode
and a second electrode and generating an elliptical vibration
according to a driving voltage applied through the first and second
electrodes, the driving and control apparatus comprising: a
controller for controlling a selection of the first channel or the
second channel as a driving channel, the first channel and the
second channel being connected to the first electrode and the
second electrode, respectively; a switch part for selecting one of
the first and second channels as the driving channel and the other
as a detection channel according to the channel selection control
of the controller, and supplying the driving voltage to the
piezoelectric ultrasonic motor through the selected driving
channel; a phase detector for detecting a voltage outputted from
the piezoelectric ultrasonic motor through the detection channel,
calculating a phase deviation representing that a phase difference
between an oscillation voltage having two times the frequency of
the driving voltage and the detection voltage is out of 90.degree.,
and outputting a phase difference voltage corresponding to the
phase deviation; a voltage controlled oscillator for generating the
oscillation voltage and controlling a phase of the oscillation
voltage according to the phase difference voltage outputted from
the phase detector; and a frequency divider for dividing the
oscillation voltage from the voltage controlled oscillator by two
to generate the driving voltage, and supplying the divided
oscillation voltage to the piezoelectric ultrasonic motor through
the driving channel.
2. The driving and control apparatus of claim 1, further comprising
a low pass filter for removing power noise and AC component
contained in the phase difference voltage outputted from the phase
detector.
3. The driving and control apparatus of claim 1, wherein the switch
part comprises: a first switch for connecting an output terminal of
the voltage controlled oscillator to the first channel connected to
the first electrode of the piezoelectric ultrasonic motor according
to the channel selection control of the controller; and a second
switch for connecting the output terminal of the voltage controlled
oscillator to the second channel connected to the second electrode
of the piezoelectric ultrasonic motor.
4. The driving and control apparatus of claim 1, wherein the phase
detector comprises: a first AND gate for ANDing the driving voltage
and the detection voltage; a second AND gate for ANDing an output
signal of the first AND gate and the oscillation voltage to detect
a phase difference between the driving voltage and the detection
voltage; and a phase difference voltage generating unit for
calculating the phase deviation, in which the phase difference is
out of 90.degree. by the second AND gate, and outputting the phase
difference voltage corresponding to the phase deviation.
Description
RELATED APPLICATION
[0001] The present application is based on, and claims priority
from, Korean Application Number 2005-106147, filed Nov. 07, 2005,
the disclosure of which is hereby incorporated by reference herein
in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a driving and control
apparatus of a piezoelectric ultrasonic motor, and more
particularly, to a driving and control apparatus of a piezoelectric
ultrasonic apparatus, which supplies the driving voltage through
one of the two electrodes of the piezoelectric ultrasonic motor
generating the elliptical vibration, detects the voltage through
the other electrode, and making the phase difference between the
driving voltage and the detection voltage be zero in a phase locked
loop (PLL) scheme, thereby achieving the operation more
efficiently.
[0004] 2. Description of the Related Art
[0005] Generally, a piezoelectric device generates a strain or
voltage when an electric field or a stress is applied thereto. A
piezoelectric stator using the piezoelectric device is driven at a
resonance frequency ranging from several tens of kHz to several
hundreds of kHz and can provide a rotor with a strain amplified by
a stack or strain expansion structure. Such a piezoelectric stator
may use itself as a vibrator, or may be used in combination with a
structure with a specific shape.
[0006] A piezoelectric ultrasonic motor using the piezoelectric
device is called a traveling wave, surface wave, or surfing type
motor. The piezoelectric ultrasonic motor is driven by a principle
of superposing two driving waves with a predetermined phase
difference.
[0007] FIG. 1 is a block diagram illustrating a conventional
driving and control apparatus of a piezoelectric ultrasonic
motor.
[0008] Referring to FIG. 1, the conventional driving and control
apparatus includes a frequency/phase controller 10, a high-speed
inverter 20, a pulse encoder 40, a current-voltage phase difference
detector 50, and a microcontroller 60. The frequency/phase
controller 10 receives frequency and phase information to generate
square waves with respect to two phases. The high-speed inverter 20
converts the square waves into AC voltages with respect to the two
phases and provides the AC voltages to an ultrasonic motor 30. The
pulse encoder 40 accesses and encodes information about the
frequency and phase applied to the ultrasonic motor 30. The
current-voltage phase difference detector 50 detects a phase
difference between a voltage VA and a current IA applied to the
ultrasonic motor 30 and outputs the detected phase difference in a
form of an impedance phase angle. The microcontroller 60 receives
the impedance phase angle from the current-voltage phase difference
detector 50 to output the frequency and phase information for
making the ultrasonic motor 30 follow the resonance frequency of
the ultrasonic motor 30.
[0009] The driving and control apparatus of the piezoelectric
ultrasonic motor is disclosed in Korean Laid-Open Patent
Publication No. 2002-0055465.
[0010] However, the conventional driving and control apparatus has
to generate two driving waves in order to drive the piezoelectric
ultrasonic motor, and also requires a current detector and/or a
voltage detector in order to detect the current and the voltage.
Thus, the conventional driving and control apparatus has a problem
in that its structure is complicated and its manufacturing cost
increases.
SUMMARY OF THE INVENTION
[0011] Accordingly, the present invention is directed to a driving
and control apparatus of a piezoelectric ultrasonic motor that
substantially obviates one or more problems due to limitations and
disadvantages of the related art.
[0012] An object of the present invention is to provide a driving
and control apparatus of the piezoelectric ultrasonic motor, which
supplies the driving voltage through one of the two electrodes of
the piezoelectric ultrasonic motor generating the elliptical
vibration, detects the voltage through the other electrode, and
making the phase difference between the driving voltage and the
detection voltage be zero in a phase locked loop (PLL) scheme,
thereby achieving the operation more efficiently.
[0013] Additional advantages, objects, and features of the
invention will be set forth in part in the description which
follows and in part will become apparent to those having ordinary
skill in the art upon examination of the following or may be
learned from practice of the invention. The objectives and other
advantages of the invention may be realized and attained by the
structure particularly pointed out in the written description and
claims hereof as well as the appended drawings.
[0014] To achieve these objects and other advantages and in
accordance with the purpose of the invention, as embodied and
broadly described herein, there is provided a driving and control
apparatus of a piezoelectric ultrasonic motor, which has a first
electrode and a second electrode and generates an elliptical
vibration according to a driving voltage applied through the first
and second electrodes. The driving and control apparatus includes:
a controller for controlling a selection of the first channel or
the second channel as a driving channel, the first channel and the
second channel being connected to the first electrode and the
second electrode, respectively; a switch part for selecting one of
the first and second channels as the driving channel and the other
as a detection channel according to the channel selection control
of the controller, and supplying the driving voltage to the
piezoelectric ultrasonic motor through the selected driving
channel; a phase detector for detecting a voltage outputted from
the piezoelectric ultrasonic motor through the detection channel,
calculating a phase deviation representing that a phase difference
between an oscillation voltage having two times the frequency of
the driving voltage and the detection voltage is out of 90.degree.,
and outputting a phase difference voltage corresponding to the
phase deviation; a voltage controlled oscillator for generating the
oscillation voltage and controlling a phase of the oscillation
voltage according to the phase difference voltage outputted from
the phase detector; and a frequency divider for dividing the
oscillation voltage from the voltage controlled oscillator by two
to generate the driving voltage, and supplying the divided
oscillation voltage to the piezoelectric ultrasonic motor through
the driving channel.
[0015] The driving and control apparatus may further include a low
pass filter for removing power noise and AC component contained in
the phase difference voltage outputted from the phase detector.
[0016] The switch part may include: a first switch for connecting
an output terminal of the voltage controlled oscillator to the
first channel connected to the first electrode of the piezoelectric
ultrasonic motor according to the channel selection control of the
controller; and a second switch for connecting the output terminal
of the voltage controlled oscillator to the second channel
connected to the second electrode of the piezoelectric ultrasonic
motor.
[0017] The phase detector may include: a first AND gate for ANDing
the driving voltage and the detection voltage; a second AND gate
for ANDing an output signal of the first AND gate and the
oscillation voltage to detect a phase difference between the
driving voltage and the detection voltage; and a phase difference
voltage generating unit for calculating the phase deviation, in
which the phase difference is out of 90.degree. by the second AND
gate, and outputting the phase difference voltage corresponding to
the phase deviation.
[0018] It is to be understood that both the foregoing general
description and the following detailed description of the present
invention are exemplary and explanatory and are intended to provide
further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiment(s) of
the invention and together with the description serve to explain
the principle of the invention. In the drawings:
[0020] FIG. 1 is a block diagram illustrating a conventional
driving and control apparatus of a piezoelectric ultrasonic
motor;
[0021] FIG. 2 is a block diagram illustrating a driving and control
apparatus of a piezoelectric ultrasonic motor according to an
embodiment of the present invention;
[0022] FIGS. 3A and 3B are block diagrams illustrating switching
operations of the driving and control apparatus of FIG. 2;
[0023] FIGS. 4A to 4D are diagrams of the piezoelectric ultrasonic
motor of FIG. 2;
[0024] FIGS. 5A and 5B are diagrams illustrating an elliptical
vibration of the piezoelectric ultrasonic motor of FIG. 2;
[0025] FIG. 6 is a graph illustrating a vibration mode of the
piezoelectric ultrasonic motor of FIG. 2;
[0026] FIG. 7 is a diagram of a phase detector of FIG. 2;
[0027] FIGS. 8A and 8B are timing diagrams illustrating an
operation of the phase detector of FIG. 7; and
[0028] FIGS. 9(a) and 9(b) are graphs illustrating a gain and a
phase difference of the piezoelectric ultrasonic motor of FIG. 2,
respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. The same reference
numerals are used to refer to the same elements throughout the
drawings.
[0030] FIG. 2 is a block diagram illustrating a driving and control
apparatus of a piezoelectric ultrasonic motor according to an
embodiment of the present invention.
[0031] Referring to FIG. 2, the driving and control apparatus
according to an embodiment of the present invention drives a
piezoelectric ultrasonic motor 100 that has a first electrode 110
(shown in FIG. 4a) and a second electrode 120(shown in FIG. 4a) and
generates an elliptical vibration by overlapping a length-direction
vibration and a curve-direction vibration according to a driving
voltage (Vdrv) applied to the first electrode 110 and the second
electrode 120. The driving and control apparatus includes a
controller 200, a switch part 300, a phase director 400, a voltage
controlled oscillator (VCO) 600, and a frequency divider 700.
[0032] A first channel CH1 and a second channel CH2 are connected
to the first electrode 110 and the second electrode 120 of the
piezoelectric ultrasonic motor 100, respectively. The controller
200 controls the switch part 300 to select one of the first and
second channels CH1 and CH2 as a driving channel.
[0033] The switch part 300 selects one of the first and second
channels CH1 and CH2 as the driving channel and the other as a
detection channel according to the channel selection control of the
controller 200. The driving voltage (Vdrv) is supplied to the
piezoelectric ultrasonic motor 100 through the selected driving
channel.
[0034] The phase detector 400 detects a voltage supplied from the
piezoelectric ultrasonic motor 100 through the detection channel.
Then, the phase detector 400 calculates a phase deviation
(.DELTA..phi.) representing that a phase difference (d.phi.)
between an oscillation voltage (Vosc) having two times the
frequency of the driving voltage and the detection voltage (Vdet)
is out of 90.degree., and outputs a phase difference voltage
corresponding to the phase deviation (.DELTA..phi.).
[0035] The VCO 600 generates the oscillation voltage (Vosc) and
controls the phase of the oscillation voltage (Vosc) according to
the phase difference voltage outputted from the phase detector
400.
[0036] The frequency divider 700 divides the oscillation voltage
(Vosc, F=2a) from the VCO 600 by two to generate the driving
voltage (Vdrv, F=a). The driving voltage (Vdrv) is supplied to the
piezoelectric ultrasonic motor 100 through the driving channel
selected by the switch part 300.
[0037] In order to supply a DC voltage in which power noise or AC
component is removed, the driving and control apparatus may further
include a low pass filter (LPF) 500 for removing the power noise or
AC component contained in the phase difference voltage outputted
from the phase detector 400.
[0038] In addition, the switch part 300 includes a first switch SW1
and a second switch SW2. According to the channel selection control
of the controller 200, the first switch SW1 connects the output
terminal of the VCO 600 to the first channel CH1, which is
connected to the first electrode of the piezoelectric ultrasonic
motor 100, and the second switch SW2 connects the output terminal
of the VCO 600 to the second channel CH2, which is connected to the
second electrode of the piezoelectric ultrasonic motor 100.
[0039] An operation of the driving and control apparatus according
to the present invention will be described below in detail. First,
the controller 200 selects one of the first channel CH1 and the
second channel CH2, which are respectively connected to the first
electrode 110 and the second electrode 120 of the piezoelectric
ultrasonic motor 100, as the driving channel according to the
user's selection. As illustrated in FIGS. 3A or 3B, the switch part
300 operates to select the first channel CH1 or the second channel
CH2 according to the channel selection control of the controller
200. The other channel that is not selected as the driving channel
serves as the detection channel.
[0040] FIGS. 3A and 3B are block diagrams illustrating the
switching operations of the driving and control apparatus of FIG.
2. Referring to FIG. 3A, when the first switch SW1 is off and the
second switch SW2 is on according to the channel selection control
of the controller 200, the first channel CH1 is selected as the
driving channel and the driving voltage (Vdrv) is supplied through
the first channel CH1 to the first electrode 110 of the
piezoelectric ultrasonic motor 100.
[0041] Referring to FIG. 3B, when the first switch SW1 is on and
the second switch SW2 is off according to the channel selection
control of the controller 200, the second channel CH2 is selected
as the driving channel and the driving voltage (Vdrv) is supplied
through the second channel CH2 to the second electrode 120 of the
piezoelectric ultrasonic motor 100.
[0042] In this manner, when the driving voltage (Vdrv) is supplied
to the piezoelectric ultrasonic motor 100, the piezoelectric
ultrasonic motor 100 generates the elliptical vibration. The
piezoelectric ultrasonic motor 100 will be described below in more
detail with reference to FIGS. 4A to 4D.
[0043] FIGS. 4A to 4D are diagrams of the piezoelectric ultrasonic
motor of FIG. 2.
[0044] Referring to FIGS. 4A to 4D, the piezoelectric ultrasonic
motor 100 includes the first electrode 110 and the second electrode
120 and causes the length-direction vibration and the
curve-direction vibration according to the driving signal applied
through the electrodes 110, 111 and 112 and the electrodes 120, 121
and 122, thereby generating the elliptical vibration.
[0045] For example, as illustrated in FIG. 4A, the piezoelectric
ultrasonic motor 100 includes a first ceramic sheet LY1, a middle
ceramic sheet LY2, and a second ceramic sheet LY3. The first
ceramic sheet LY1 has the first upper electrode 111 and the second
upper electrode 121 separated from each other on its top surface.
The middle ceramic sheet LY2 is disposed under the first ceramic
sheet LY1 and has a ground electrode 130 on its top surface. The
second ceramic sheet LY3 is disposed under the middle ceramic sheet
LY2 and has the first lower electrode 112 and the second lower
electrode 122 on its top surface and a ground electrode 130 on its
bottom surface. The electrodes 110, 111 and 112 and the electrodes
120, 121 and 122 are extended up to the outside of the ceramic
sheets LY1, LY2 and LY3 in a predetermined direction.
[0046] The ceramic sheets LY1, LY2 and LY3 are vertically stacked,
as illustrated in FIG. 4B.
[0047] Polarization directions (arrow directions) of the ceramic
sheets LY1, LY2 and LY3 are alternated in order to simultaneously
vibrate the left side of the first ceramic sheet LY1 and the right
side of the second ceramic sheet LY3, and the right side of the
first ceramic sheet LY1 and the right side of the second ceramic
sheet LY3.
[0048] FIG. 4C is a perspective view of the piezoelectric
ultrasonic motor where external electrodes are formed in the
stacked ceramic sheet structure. A first external electrode CCH1 is
formed on a first side of the stacked ceramic sheet structure to
connect the first upper electrode 111 to the second lower electrode
112, and a second external electrode CCH2 is formed on a second
side of the stacked ceramic sheet structure to connect the second
upper electrode 121 to the second lower electrode 122. In addition,
a third external electrode CG is formed on a third side of the
stacked ceramic sheet structure to connect the ground electrodes
130, which are formed on the top surface of the middle ceramic
sheet LY2 and the bottom surface of the second ceramic sheet
LY3.
[0049] Since the driving signal is simultaneously applied through
the external electrodes CCH1, CCH2 and CG to the electrodes
disposed diagonally, the ceramic sheets disposed diagonally can be
vibrated. This vibration is transferred to the outside through a
driving tip 140 formed one side of the stacked ceramic sheet
structure.
[0050] FIG. 4D illustrates a modification of the piezoelectric
ultrasonic motors 100 of FIGS. 4A to 4C.
[0051] In the piezoelectric ultrasonic motor 100' of FIG. 4D, first
ceramic sheets LY1 and middle ceramic sheets LY2 are alternately
stacked to form an upper vibration region. Here, each of the first
ceramic sheets LY1 has a first upper electrode 111 and a second
upper electrode 121 separated from each other on its top surface,
and each of the middle ceramic sheets LY2 is disposed under each of
the first ceramic sheets and has a ground electrode 130 on its top
surface.
[0052] In addition, second ceramic sheets LY3 and middle ceramic
sheets LY2 are alternately stacked under the above-described
stacked structure to form a lower vibration region. Here, each of
the second ceramic sheets LY3 has a first lower electrode 112 and a
second lower electrode 122 on its top surface, and each of the
middle ceramic sheet LY2 is disposed under each of the second
ceramic sheets LY3 and has a ground voltage 130 on its top surface.
Meanwhile, a ground electrode 130 is formed on the bottom surface
of the second ceramic sheet disposed at the lowermost position.
[0053] Polarization directions of the stacked ceramic sheets LY1,
LY2 and LY3 are alternated as illustrated in FIG. 4B. Also, the
first electrode 110, the external electrodes CCH1,CCH2 AND CG1 for
connecting the second electrode 120, and the ground electrodes 130
are formed as illustrated in FIG. 4C.
[0054] Through the external electrodes, the portions located at the
diagonal positions of the upper vibration region and the lower
vibration region can be simultaneously vibrated.
[0055] In order to generate the vibration in the portions located
at the diagonal positions, it is preferable that the number of the
ceramic sheets stacked to form the upper vibration region is
identical to the number of the ceramic sheets stacked to form the
lower vibration region, but the present invention is not limited
thereto.
[0056] Meanwhile, electrode protection sheets (not shown) covering
the electrodes may be further stacked in order to protect the
electrodes formed on the stacked ceramic sheets of FIG. 4D.
[0057] In FIG. 4, the piezoelectric ultrasonic motor 100' has the
vibration regions located in the diagonal lines among the four
vibration regions, that is, the up/down/right/left vibration
regions in the vertically stacked ceramic sheets.
[0058] However, the piezoelectric ultrasonic motor 100' used in the
driving and control apparatus according to the present invention
simultaneously generates the length-direction vibration of FIG.
5(a) and the curve-direction vibration of FIG. 5(b) by the driving
signals applied through the first and second electrodes. Therefore,
the present invention can be applied to any piezoelectric
ultrasonic motors if they generate the elliptical vibration. The
piezoelectric ultrasonic motor can have various shapes and
structures.
[0059] The vibrations at the first and second channels when the
piezoelectric ultrasonic motor generates the elliptical vibration
are illustrated in FIG. 6.
[0060] FIG. 6 is a graph illustrating a vibration mode of the
piezoelectric ultrasonic motor of FIG. 2.
[0061] It can be seen from FIG. 6 that an admittance is highest
when a "CH1" graph and a "CH2" graph have a phase difference of
90.degree.. The admittance is an index representing how well the
signal flows. That is, it can be seen that the vibration efficiency
is high when the piezoelectric ultrasonic motor has the phase
difference of 90.degree..
[0062] Referring again to FIG. 2, the phase detector 400 detects
the voltage outputted from the piezoelectric ultrasonic motor 100
through the detection channel, calculates the phase deviation
(.DELTA..phi.) representing that a phase difference (d.phi.)
between an oscillation voltage (Vosc) having two times the
frequency of the driving voltage and the detection voltage (Vdet)
is out of 90.degree., and outputs a phase difference voltage
corresponding to the phase deviation (.DELTA..phi.).
[0063] The VCO 600 generates the oscillation voltage (Vosc) having
the preset frequency (F=2a) and controls the phase of the driving
voltage (Vdrv) according to the phase difference voltage outputted
from the phase detector 400.
[0064] The frequency divider 700 divides the oscillation voltage
(Vosc) outputted from the VCO 600 by two to generate the driving
voltage (Vdrv). The driving voltage (Vdrv) is supplied to the
piezoelectric ultrasonic motor 100 through the driving channel
selected by the switch part 300.
[0065] The driving and control apparatus including the LPF 500 can
remove the power noise or AC component contained in the phase
difference voltage, thereby providing the clearer phase difference
voltage.
[0066] FIG. 7 is a diagram of the phase detector of FIG. 2.
[0067] Referring to FIG. 7, the phase detector 400 includes a first
AND gate 410 for ANDing the driving voltage (Vdrv, F=2a) and the
detection voltage (Vdet), a second AND gate 420 for ANDing an
output signal of the first AND gate 410 and the oscillation voltage
(Vosc, F=2a) to detect the phase difference (.DELTA..phi.) between
the driving voltage (Vdrv) and the detection voltage (Vdet), and a
phase difference voltage generating unit 430 for calculating the
phase deviation (.DELTA..phi.) in which the phase difference
(d.phi.) is out of 90.degree. by the second AND gate 420 and
outputting the phase difference voltage corresponding to the phase
deviation (.DELTA..phi.).
[0068] FIGS. 8A and 8B are timing diagrams illustrating an
operation of the phase detector of FIG. 7. An operation of the
phase detector will be described below reference to FIGS. 7 and
8.
[0069] Referring to FIGS. 7 and 8A, when the first channel CH1 is
selected as the driving channel, the first AND gate 410 performs
the logic AND operation on the driving voltage (Vdrv) and the
detection voltage (Vdet). The second AND gate 420 performs the
logic AND operation on the output signal A of the first AND gate
410 and the oscillation voltage (Vosc) to detect the phase
difference (d.phi.) between the driving voltage (Vdrv) and the
detection voltage (Vdet), and outputs the detected phase difference
(d.phi.) C to the phase difference voltage generating unit 430. The
phase difference voltage generating unit 430 calculates the phase
deviation (.DELTA..phi.) and outputs the phase difference voltage
to the LPF 500.
[0070] When the phase difference (d.phi.=d.phi.1-d.phi.2) is less
than 90.degree., that is, when the phase deviation
(.DELTA..phi.=d.phi.-90.degree.) is negative, the phase difference
signal (d.phi.) C outputted from the second AND gate 420 has no
pulse, as illustrated in FIG. 8A. Therefore, the phase difference
voltage generating unit 430 recognizes that there is no phase
deviation. In this case, the VCO 600 has to decrease the
frequency.
[0071] On the other hand, when the phase difference
(d.phi.=d.phi.1-d.phi.2) is greater than 90.degree., that is, when
the phase deviation (.DELTA..phi.=d.phi.-90.degree.) is positive,
the phase difference signal (d.phi.) C outputted from the second
AND gate 420 has a predetermined pulse, as illustrated in FIG. 8B.
Then, the generation of the phase deviation is notified to the
phase difference voltage generating unit 430. At this point, the
phase difference voltage generating unit 430 generates the phase
difference voltage according to the predetermined pulse. In this
case, the VCO 600 has to increase the frequency.
[0072] FIGS. 9(a) and 9(b) are graphs illustrating a gain and a
phase difference of the piezoelectric ultrasonic motor of FIG. 2,
respectively.
[0073] Specifically, FIG. 9(a) is a graph illustrating the gain of
the piezoelectric ultrasonic motor. When the second channel CH2 is
selected as the driving channel, the gain (V1/V2) of the
piezoelectric ultrasonic motor 100 is given by the "G1" graph. The
gain (V1/V2) of the piezoelectric ultrasonic motor 100 means the
ratio of the output voltage (V1) to the input voltage (V2).
[0074] When the first channel CH1 is selected as the driving
channel, the gain (V2/V1) of the piezoelectric ultrasonic motor 100
is given by the "G2" graph. The gain (V2/V1) of the piezoelectric
ultrasonic motor 100 means the ratio of the output voltage (V2) to
the input voltage (V1).
[0075] FIG. 9(b) is a graph illustrating the phase difference of
the piezoelectric ultrasonic motor. When the second channel CH2 is
selected as the driving channel, the phase difference
(.phi.1-.phi.2) between the input voltage (V2) and the output
voltage (V1) is almost 90.degree.. When the first channel CH1 is
selected as the driving channel, the phase difference
(.phi.2-.phi.1) between the input voltage (V1) and the output
voltage (V2) is almost 90.degree..
[0076] As described above, the driving and control apparatus of the
piezoelectric ultrasonic motor supplies the driving voltage through
one of the two electrodes of the piezoelectric ultrasonic motor
generating the elliptical vibration, detects the voltage through
the other electrode, and making the phase difference between the
driving voltage and the detection voltage be zero in a phase locked
loop (PLL) scheme, thereby achieving the operation more
efficiently. Since the driving and control apparatus is implemented
more simply, its manufacturing cost can be reduced.
[0077] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention.
Thus, it is intended that the present invention covers the
modifications and variations of this invention provided they come
within the scope of the appended claims and their equivalents.
* * * * *